The present invention is directed, in general, to an internal combustion engine and, more specifically, to a rotary internal combustion engine having a rotor that is directly coupled to a drive shaft without eccentric gearing.
A conventional internal combustion reciprocating engine converts reciprocating motion of a piston within a cylinder into rotating motion via a crankshaft having offset sections coupled to a connecting rod mechanism. While long the standard for internal combustion engines, a four-stroke, or four-cycle, internal combustion reciprocating engine creates power by causing a metal piston to move up and down twice per combustion cycle in a cylinder bore, thereby varying the instantaneous size of the combustion chamber, to achieve one power stroke. This often vertical or inclined motion is changed to a rotational flywheel motion by connecting the piston to an eccentric portion of the crankshaft with a connecting rod. Inertial forces at the top and bottom of each stroke of the reciprocating piston invariably cause vibration and high internal stresses on the engine components. These vibrations and stresses increase with increasing crankshaft angular velocity measured in revolutions per minute (rpm). Only about 50 to 60 percent of total combustion gas pressure exerted on the piston is converted into useable output torque of the crankshaft due primarily to the characteristics of the crank/connecting rod mechanism. In a conventional reciprocating engine essentially all of the pressure generated by the combustion is useful in pushing the piston to do work. However, much of the energy lost in a conventional reciprocating engine is caused by the redirection of a linear motion of the piston into a rotary motion of the crankshaft.
Due to a valve overlap period in which both the intake valve and the exhaust valve are open even after exhaust is expelled, a small amount of combustion gas remains in the combustion chamber and, therefore, it is difficult to both improve on the combustibility of the mixture and to decrease the amount of unburned gas. Meanwhile, the structure of the crank mechanism and valve operating mechanism, that is: the camshaft, intake valves and exhaust valves; is quite complex and requires precise adjustment. It is therefore difficult to decrease vibration and noise caused by the reciprocating motion of the piston. It is also difficult to revise the size of the four-cycle reciprocating engine without decreasing the output horsepower of the engine.
An alternative embodiment of the internal combustion engine that has enjoyed significant development is the rotary engine. The rotary engines of interest are not to be confused with the rotary aircraft engines of the early 20th Century. These rotary aircraft engines comprise a crankshaft fixed to the aircraft structure and a plurality of cylinders radially positioned about the crankshaft such that the crankshaft remains fixedly coupled to the vehicle, in this instance an aircraft, while the engine block, cylinders and pistons, rotate about the crankshaft. The propeller is fixedly coupled to the engine block and rotates with the engine block assembly. By contrast, the rotary engine used in automotive applications employs an engine block fixed to the vehicle and an internally rotating xe2x80x9cpistonxe2x80x9d that causes a drive shaft to rotate relative to the vehicle.
Accordingly, until present, various kinds of rotary-piston type internal combustion engines, also know as rotary piston engines, have been proposed. More specifically, rotary piston engines can be classified as either: (a) direct-rotation type rotary piston engines having a rotor rotating coaxially with the output shaft or, (b) planetary-rotation type rotary piston engines having a rotor geared to and rotating eccentrically about the output shaft. As the structure of classical approaches to the former, i.e., direct-rotation engines, has generally been believed to be more complex than that of the latter, i.e., planetary-rotation engines, the former has generally not been put into practical use. However, the Wankel rotary piston engine, an example of the planetary-rotation engine has seen considerable development and has been put to practical use since the 1930""s.
In the Wankel rotary engine, an arciform deltoid rotor is held within a rotor holding bore which has an inner surface cross section that is similar to a peritrochoidal curve. The conformance to a peritrochoidal profile is driven by the requirement that all three bearing points of the Wankel rotor remain in constant contact with the inner surface of the engine. The rotor is rotated in a planetary motion through the engaging of a rotor gear on the rotor with a gear on an output shaft. The location of the arciform deltoid rotor within the rotor holding bore creates three chambers therein. Depending on the planetary motion of the rotor, while the chambers outside of the rotor vary their capacities, four strokes of intake (suction), compression, combustion (expansion) and exhaust are performed. Because of the peritrochoidal chamber, the Wankel has an exhaust cavity immediately following the ignition point that rapidly enlarges. This causes a significant portion of the gas pressure to be lost as expansion within the enlarging cavity, and not converting the expansion pressure into useable torque. It is also notable that in the Wankel engine, the combustion gas pressure is exerted on both: (a) a pressure-receiving rotor surface facing, but just rotationally beyond, the point of combustion, and (b) a trailing portion of the rotor surface facing, but that is rotationally before the point of combustion. This pressure on the trailing portion of the rotor surface effectively attempts to drive the rotor in reverse, thereby reducing the engine efficiency. Therefore, it is generally accepted that only about 60 to 70 percent of the combustion gas pressure received by the rotor can be converted into output torque. Significantly, the architecture of the Wankel engine, i.e., a peritrochoidal section, makes it difficult to improve the combustibility in the combustion stroke and to decrease the exhaust quantity of unburned gases.
Until present, various types of direct-rotation rotary engines have been proposed. FIGS. 12-17 show highly schematic, well-known, direct-rotation rotary engines 300A-300F. FIG. 18 shows a direct-rotation rotary engine 300G put into practical use by Malorie Co. This engine 300G has a housing 300, a rotor 301, a suction port 302, an ignition plug 303, an exhaust port 304 and a scavenging port 305 with the rotor 301 rotating clockwise. An engine 300H shown in FIG. 18 is provided with a housing 310, a suction port 311, an exhaust port 312, a rotor holding bore 313, a rotor 314 coaxial with the bore 313, cycloid tooth portions 315, 316 formed on the rotor 314, a first small cylindrical driven rotor 317, a second small cylindrical driven rotor 318, a combustion subchamber 323 and an exhaust chamber 324. A prototype of this engine 300H made in about 1945 was reported to have high output horse power performance notwithstanding its small and light structure. However, the engine was not put into practical use after its development.
Next, descriptions will be given concerning technical problems of the above prior art. In the various direct-rotation engines 300A-300F shown in FIGS. 12-17, the axial center of the rotor is eccentric to the axial center of the rotor holding bore, and presumably some portion of the combustion gases will generate an intrinsically reverse-driving torque. Thus, it is difficult to improve the efficiency in converting the combustion gas pressure into output torque. For an engine having plural cylinders, a straight output shaft cannot be applied, and moreover, the structure of the output shaft becomes complicated and engine vibrations will occur due to this eccentric structure.
Other problems include: (a) difficulty in providing adequate durability of gas sealing members and engine parts, (b) some of the above engines also require an intake valve and an exhaust valve, and (c) difficulty in sufficiently lengthening the suction period and the exhaust period. In the direct-rotation rotary engine 300 shown in FIG. 18, the structure is complex due to its many components, and thus manufacturing costs become high. The direct rotation rotary engine 300H shown in FIG. 19 is superior due to its simple structure, yet there remain some problems in the reliability and durability of gas sealing mechanisms between the cycloid tooth portions and small cylinders. Also, it is difficult to sufficiently lengthen the periods of suction stroke and exhaust stroke which are opposed at 180 degrees of the rotor rotation angle.
Accordingly, what is needed in the art is an internal combustion engine that does not suffer from the deficiencies of the prior art while taking advantage of the energy conversion efficiency of a direct-rotation rotary engine.
To address the above-discussed deficiencies of the prior art, the present invention provides an internal combustion engine and a method of manufacturing the internal combustion engine. The internal combustion engine comprises a housing, a first rotor, first and second impellers and a compression cam. In a preferred embodiment, the housing has a first inner surface defining a first cavity therein, the first rotor is journalled for rotation within the first cavity and is situated to define compression and exhaust cavities on opposing sides therein, first and second impellers located in, and slidable with respect to, first and second opposing radial apertures in the first rotor, and the compression cam is fixedly coupled to the housing. The compression cam has a working surface portion that corresponds to a profile of the inner surface to force the first and second impellers to contact the inner surface and a dead surface portion that departs from the profile to allow the first and second impellers to withdraw from the inner surface.
Thus, in a global sense, the present invention provides a direct-rotation, internal combustion, rotary engine comprising a symmetrical rotor that rotates concentrically within a cavity of an engine housing. The rotor includes two opposing radial apertures wherein are located two impellers that ride upon a working surface of a cam and contact the inner surface of the cavity during compression and power strokes, and a dead surface portion wherein the impellers withdraw from the inner surface between the compression and power strokes.
In a preferred embodiment, the profile has a modified peritrochoidal form. In one embodiment, a peripheral surface of the first rotor seals against at least a portion of the inner surface. In a preferred embodiment, the first rotor comprises an outer flywheel and an inner hub and the engine further comprises a drive shaft having a longitudinal axis coincident a central axis of the housing. The drive shaft is coupled to the inner hub; and the outer flywheel has the first and second opposing radial apertures therethrough.
In another embodiment, the internal combustion engine further comprises a lubrication system coupled to front and rear engine covers and in fluid communication with the first rotor and the compression cam. In one embodiment, the compression cam is coupled the front engine cover and the engine further comprises an combustion cam coupled the first rotor.
In another embodiment, the internal combustion engine further comprises a fuel metering system coupled the housing and in fluid communication with the compression cavity and the exhaust cavity. In yet another embodiment, the internal combustion engine further comprises an ignition system coupled the housing and configured to ignite a fuel/air mixture in the ignition chamber.
In one embodiment, the internal combustion engine further comprises an intake aperture through the housing and in fluid communication between the atmosphere and the compression cavity, and an exhaust aperture through the housing and in fluid communication between the atmosphere and the exhaust cavity. In yet another embodiment, the internal combustion engine further comprises a cooling system coupled the housing.
The present invention further provides an internal combustion system comprising an internal combustion engine, as described, and a transmission coupled to the internal combustion engine.
The foregoing has outlined, rather broadly, preferred and alternative features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.